Missouri’s Columbia. Ivair Valmorbida, a state agricultural entomologist at the University of Missouri Extension, has verified the existence of a novel soybean pest in Missouri.
In the first week of August, Valmorbida confirmed the presence of soybean tentiform leafminer in soybean fields in central Missouri. When the pest was discovered, MU Extension agronomist Todd Lorenz was in the field. Only one of the more than 70 fields studied so far had the insect, according to MU Extension scientists, but its existence is alarming, adds Valmorbida.
Macrosaccus morrisella, a soybean tentiform leafminer, was found to feed on soybeans in Minnesota and the Dakotas in 2021 and Nebraska in 2024.
It consumes two natural plants, the American hogpeanut and the slick fuzzybean, which belong to the same family as soybeans, according to the University of Minnesota, adds Valmorbida.
This pest is a tiny, white larva that eventually turns pale green. The mature moths have gray-black markings on their orange and white wings and are less than an inch long.
On the underside of soybean leaves, adults deposit their eggs. Larvae produce mines that do not pass through the main lateral veins or midribs of the leaves by feeding inside the leaves and tunneling. Like defoliation, the mined tissue eventually dies, reducing the leaf area.
Mines grow from little, linear ones to larger, oval, elongated white spots on the underside of the leaves. On the upper surface of the leaves, these mines become tentiform, or slightly elevated. The soybean tentiform leafminer is typically found in wooded regions and along field borders.
Although there are no known management strategies for this insect, researchers from the University of Minnesota suggest that translaminar pesticides, natural enemies of the leafminer, and a number of parasitic wasps could be effective.
Valmorbida advises farmers who suspect the presence of tentiform leafminer to scout soybean fields and get in touch with their local MU Extension agronomist. Valmorbida can also be reached by farmers at [email protected] or 573-882-6446.
To find out where tentiform leafminer is found in soybean fields, Valmorbida is collaborating with other academic institutions. The Soybean Tentiform Leafminer in Minnesota Soybean publication from the University of Minnesota can be found at https://extension.umn.edu. Additionally, CropWatch, a resource offered by the University of Nebraska Lincoln, offers updates on tentiform leafminer and other pests at https://cropwatch.unl.edu.
